Questions: transaction log and commit
Date: 1996/05/30
Message-ID: <4oisuh$ggo_at_tst.hk.super.net>#1/1
Hi all Oracle gurus,
I have a question about the transaction log which have
puzzled me for a long time. What I know about the
relationship between the transaction log and the commit is
that, when a user do a commit, the transaction log buffer in
the SGA will be immediately flushed into the disc so that
if the DB crash, we can still recover the transaction made by
following the transaction log.
However, when the Oracle DB engine issue a OS call asking
for a write service, the OS may pend this call and store
the data in the cache, waiting for a batch write. So
what may happen is that when a user do a commit, the log
in the SGA which is supposed to be written to the disc
immediately, is still in the OS cache buffer, awaiting
to be flushed to the disc. If the machine shutdown at
this point, then the log will not be written to the disc
and we cannot recover the data after a commit.
Is there something wrong with the above reasoning? Can
anyone tell me if this will be a potential danger to data
loss?
Thx a lot.
KP.
--
Poon Kin-Lin. kpoon_at_hk.super.net http://www.hk.super.net/~kpoon
852.252.56.531
Received on Thu May 30 1996 - 00:00:00 CEST